CVE-2026-11352 QUIC zero-length UDP datagrams busy-loop
A malicious HTTP/3 server can cause a remote denial of service against curl clients by streaming zero-length UDP datagrams, stalling the QUIC receive loop.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-11352?
CVE-2026-11352 is a high-severity denial of service vulnerability in Haxx Curl, published on 3 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
An issue in curl’s QUIC UDP receive function allows a malicious HTTP/3 server to trigger a remote denial of service against a curl or libcurl client. Because the helper function discards zero-length UDP datagrams before counting them toward the per-call packet budget, a connected QUIC peer can continuously stream empty datagrams to indefinitely stall the client.
Weakness: CWE-835
Which versions are affected by CVE-2026-11352?
It affects 1 product.
Products include Haxx Curl.
How do I fix CVE-2026-11352?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-11352 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-11352 exists.
Other vulnerabilities in Haxx Curl
Sources
Also known as ALPINE-CVE-2026-11352, BELL-CVE-2026-11352, CURL-CVE-2026-11352, DEBIAN-CVE-2026-11352, GHSA-qxwx-hr5v-h5q4, JLSEC-2026-1198 and 3 more.